Advanced search
Start date

Study of GABAergic modulation in the circuitry involved in analgesia induced by electrical stimulation of the island cortex.

Full text
Heloisa Alonso Matielo
Total Authors: 1
Document type: Master's Dissertation
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
Defense date:
Examining board members:
Camila Squarzoni Dale; Abrahão Fontes Baptista; Rosana de Lima Pagano; Andréa da Silva Torrão
Advisor: Camila Squarzoni Dale

Neuropathic pain presents itself as one of the most difficult conditions for antalgic treatment, as it has a chronic character and impairs the general quality of life, which requires brandnew effective treatments. Neurostimulation has the ability to alter the activity of pain modulatory pathways, potentially promoting analgesia. In this context, it has been demonstrated that electrical stimulation of the insular cortex (ESI) induces antinociception as well as it influences neuronal activity of brain areas, pointing insula as na iminente target for pain modulation. Herein, we aimed to evaluate the participation of GABAergic neurotransmission in repetitive ESI antinociceptive effects, to evaluate neuroplasticity and astrocytic cell alterations, as well as assess the presence of excitatory and inhibitory projections between the insula and the anterior cingulate cortex (ACC). Male Sprague Dawley rats (280-340g; CEUA 3447131117) submitted to chronic constriction of the sciatic nerve in the right side (CCI) received a concentric electrode on the left posterior insula (1.0 mm caudal to bregma, 5.8 mm laterality, 7.1 mm deep) and underwent five consecutive daily stimulations (15 min, 60 Hz, 210 s, 1V). GABAA receptor antagonist, bicuculline methiodide, (0.1ug, i.t) administered 1h prior to the paw pressure test, induced reversion of the ESI-induced antinociception, without altering the general activity in the open field test. Increase of GAD65 in the insula after ESI was observed by immunofluorescence, without changes of GFAP, synaptophysin and/or tyrosine hydroxylase (TH) in insula, hippocampus, anterior and mid cingulate cortex, Periaqueductal Gray (PAG) and rostral ventromedial medulla (RVM). Western blotting analysis, revealed no changes in GAD65 after ESI. GABA, glutamate and glycine levels analyzed by high performance liquid chromatography (HPLC) did not change after EECI. In collaboration with the University of Calgary, GAD2Crex Ai9, PVCrexAi9, Vglut2CrexAi9 mice underwent Spared Nerve Injury (SNI) and injection of tract tracer choleric toxin-subunit B (CTB488). It has been demonstrated the presence of GABAergic, parvalbumin positive (PV+) and glutamatergic projections between the insula and the ACC, which were not activated by c-Fos in an immunofluorescence assay. GAD2-cre, PV-cre, and Vglut2-cre mice received adeno-associated viral titers for opsin expression (pAAV9-EF1a-DIO-hChR2 (H134R) -eYFP) in insula and a fiberoptic cannula was implanted in right insula (0.5 mm posterior to the bregma, 0.375 laterality, 4.0 mm deep) or right ACC (1.055 mm anterior to the bregma, 0.255 mm laterality, 1.522 mm deep). The animals underwent SNI surgery on the left sciatic nerve. 6 to 8 weeks after virus injection, animals were subjected to optostimulation (DPSS blue lasers 472 nm, 5 mW, 10 Hz or 40 Hz). Only the optogenetic activation of PV + neurons induced conditioned place preference, without changing the mechanical threshold in the Digital Plantar Anesthesiometer (DPA). The results obtained point out that GABAergic signaling partially participates in ESI-induced antinociception, as well as demonstrates the presence of GABAergic, PV + and glutamatergic projections between the insula and the ACC, and their influence on pain modulation in neuropathic pain models. (AU)

FAPESP's process: 17/25399-4 - Study of GABAergic modulation in the circuitry involved in analgesia induced by the electrical stimulation of the insular cortex
Grantee:Heloísa Alonso Matielo
Support Opportunities: Scholarships in Brazil - Master